Hash Cracking

Summary

• Hashcat
  • Hashcat Example Hashes
  • Hashcat Install
  • Mask attack
  • Dictionary
• John
  • Usage
• Rainbow tables
• Tips and Tricks
• Online Cracking Resources
• References

Hashcat

Hashcat Install

apt install cmake build-essential -y
apt install checkinstall git -y
git clone https://github.com/hashcat/hashcat.git && cd hashcat && make -j 8 && make install

1. Extract the hash
2. Get the hash format: hashcat.net/example_hashes
3. Establish a cracking stratgy based on hash format (ex: wordlist -> wordlist + rules -> mask -> combinator mode -> prince attack -> …)
4. Enjoy plains
5. Review strategy
6. Start over

Dictionary

Every word of a given list (a.k.a. dictionary) is hashed and compared against the target hash.

hashcat --attack-mode 0 --hash-type $number $hashes_file $wordlist_file -r $my_rules

• Wordlists

  • packetstorm
  • weakpass_3a
  • weakpass_3
  • Hashes.org
  • kerberoast_pws
  • hashmob.net
  • clem9669/wordlists

• Rules

  • One Rule to Rule Them All
  • nsa-rules
  • hob064
  • d3adhob0
  • clem9669/hashcat-rule

Mask attack

Mask attack is an attack mode which optimize brute-force.

Every possibility for a given character set and a given length (i.e. aaa, aab, aac, …) is hashed and compared against the target hash.

# Mask: upper*1+lower*5+digit*2 and upper*1+lower*6+digit*2 
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 ?u?l?l?l?l?l?d?d
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 ?u?l?l?l?l?l?l?d?d 
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 -1 "*+!??" ?u?l?l?l?l?l?d?d?1
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 -1 "*+!??" ?u?l?l?l?l?l?l?d?d?1 

# Mask: upper*1+lower*3+digit*4 and upper*1+lower*3+digit*4
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 ?u?l?l?l?d?d?d?d
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 ?u?l?l?l?l?d?d?d?d
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 ?u?l?l?l?l?l?d?d?d?d
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 -1 "*+!??" ?u?l?l?l?d?d?d?d?1
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 -1 "*+!??" ?u?l?l?l?l?d?d?d?d?1

# Mask: lower*6 + digit*2 + special digit(+!?*)
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 -1 "*+!??" ?l?l?l?l?l?l?d?d?1
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 -1 "*+!??" ?l?l?l?l?l?l?d?d?1?1

# Mask: lower*6 + digit*2
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 /content/hashcat/masks/8char-1l-1u-1d-1s-compliant.hcmask
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 -1 ?l?d?u ?1?1?1?1?1?1?1?1

# Other examples
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 ?a?a?a?a?a?a?a?a?a
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 ?a?a?a?a?a?a?a?a 
hashcat -m 1000 --status --status-timer 300 -w 4 -O /content/*.ntds -a 3 ?u?l?l?l?l?l?l?d?d?d?d
hashcat --attack-mode 3 --increment --increment-min 4 --increment-max 8 --hash-type $number $hashes_file "?a?a?a?a?a?a?a?a?a?a?a?a"
hashcat --attack-mode 3 --hash-type $number $hashes_file "?u?l?l?l?d?d?d?d?s"
hashcat --attack-mode 3 --hash-type $number $hashes_file "?a?a?a?a?a?a?a?a"
hashcat --attack-mode 3 --custom-charset1 "?u" --custom-charset2 "?l?u?d" --custom-charset3 "?d" --hash-type $number $hashes_file "?1?2?2?2?3"

John

John Usage

# Run on password file containing hashes to be cracked
john passwd

# Use a specific wordlist
john --wordlist=<wordlist> passwd

# Use a specific wordlist with rules
john --wordlist=<wordlist> passwd --rules=Jumbo

# Show cracked passwords
john --show passwd

# Restore interrupted sessions
john --restore

Rainbow tables

The hash is looked for in a pre-computed table. It is a time-memory trade-off that allows cracking hashes faster, but costing a greater amount of memory than traditional brute-force of dictionary attacks. This attack cannot work if the hashed value is salted (i.e. hashed with an additional random value as prefix/suffix, making the pre-computed table irrelevant)

Tips and Tricks

• Cloud GPU
  • penglab - Abuse of Google Colab for cracking hashes. 🐧
  • google-colab-hashcat - Google colab hash cracking
  • Cloudtopolis - Zero Infrastructure Password Cracking
  • Nephelees - also a NTDS cracking tool abusing Google Colab
• Build a rig on premise
  • Pentester’s Portable Cracking Rig - $1000
  • How To Build A Password Cracking Rig - 5000$
• Online cracking
  • Hashes.com
  • hashmob.net: great community with Discord
• Use the loopback in combination with rules and dictionary to keep cracking until you don’t find new passsword: hashcat --loopback --attack-mode 0 --rules-file $rules_file --hash-type $number $hashes_file $wordlist_file
• PACK (Password Analysis and Cracking Kit)
  • iphelix/pack
  • Can produce custom hcmask files to use with hashcat, based on statistics and rules applied on an input dataset
• Use Deep Learning
  • brannondorsey/PassGAN

Online Cracking Resources

• hashes.com
• crackstation.net
• hashmob.net

References

• Cracking - The Hacker Recipes
• Using Hashcat to Crack Hashes on Azure
• miloserdov.org hashcat
• miloserdov.org john
• DeepPass — Finding Passwords With Deep Learning - Will Schroeder - Jun 1